import java.util.Scanner;

public class Three {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n=in.nextInt(),m=in.nextInt(),x=in.nextInt(),y=in.nextInt();
        long[][] dp=new long[n+2][m+2];
        dp[0][1]=1;
        x+=1;
        y+=1;
        for (int i = 1; i <= n+1; i++) {
            for (int j = 1; j <=m+1; j++) {
                if(i!=x&&j!=y&&Math.abs(i-x)+Math.abs(j-y)==3||(i==x&&j==y)){
                    dp[i][j]=0;
                }else {
                    dp[i][j]=dp[i-1][j]+dp[i][j-1];
                }
            }
        }
        System.out.println(dp[n+1][m+1]);
    }
}
